Paint delivery systems utilized for the finishing of a wide variety of manufactured items such as motor vehicles, household appliances and the like are becoming increasingly more sophisticated. A typical industrial paint delivery system may comprise a central paint supply having a number of painting stations communicating therewith. Such systems can selectively deliver a variety of different paints to a given painting station and include complex fluid pathways having a number of tanks, pumps, and conduits. These paint delivery systems tend to accumulate deposits in the course of their use and such deposits can decrease, and even block, the flow of paint therethrough. The deposits are comprised of pigment, resins and other components of the paint. In addition to causing clogging, such deposits can also contaminate the paint color, and can break loose and cause surface defects in the finished, painted product. Accordingly, it is necessary to periodically clean the paint delivery system.
Because of the complexity of such systems, and because of the necessity of avoiding expensive down time, it is generally preferable that the systems be cleaned without disassembly. Typically, systems are cleaned by passing a variety of solvents, detergents or other such materials therethrough. Prior art processes usually involve numerous steps and multiple cleaning compositions; and such processes frequently do not provide full removal of deposits, particularly hardened pigment residues.
A typical prior art process can involve flushing five or more different cleaning compounds of varying polarity through the paint system and can include up to thirty separate operational steps. The numerous cleaning compounds and steps are needed in order to fully remove all deposits from the system and to insure compatibility of any traces of cleaning compounds remaining in the system with subsequently introduced paint. As a result, the system must be sequentially rinsed with various materials in a predetermined order.
Clearly, it would be desirable to have a single cleaning composition which is capable of effectively removing all deposits from a paint delivery system. It is further desirable that this single composition be capable of dissolving a variety of different paint residues, and that the composition not harm components of the paint delivery system or leave any residue which would contaminate paint when the system is subsequently put back into service.
U.S. Pat. Nos. 4,537,705 and 4,594,176 both disclose aqueous based paint stripping compositions. These compositions include an alkaline material together with a particular group of polyamines. The compositions can optionally include small amounts of accelerator compounds which may comprise glycol ethers. U.S. Pat. No. 4,421,680 discloses an aqueous based degreaser composition which includes a glycol ether, a long chain amide, a detergent, sodium metasilicate and an alkali such as potassium hydroxide. While these compounds have some utility, they are not capable of dissolving heavy deposits of the type encountered in the lines of paint delivery systems.
One prior art approach to the problem of paint line cleaning is disclosed in U.S. Pat. No. 4,968,447. Shown therein, is a paint line cleaning composition which is of relatively low viscosity and which includes an organic solvent having a particulate, polymeric material dispersed therein. The polymeric material provides a mild abrasive action which scrubs away paint residue as the liquid is pumped through the paint delivery system. While this composition efficiently removes a variety of paint deposits, there are instances in which the particulate material has been found to interfere with the mechanical operation of some components of some paint delivery systems, and there is a need for a particulate-free composition which will effectively remove a variety of paint deposits. Also, in some instances it is not possible, or practical, to pump the cleaning composition of the '447 patent through equipment which is to be cleaned, and there is therefore a further need for a cleaning composition which does not require any flow, or high degree of agitation to effect cleaning. Finally, it is essential that any cleaning composition be of low toxicity and present a minimal hazard of fire, explosion or such undesirable chemical reaction.
The present invention provides a cleaning composition which is non-abrasive and safe, and which effectively dissolves a wide variety of solvent based and water based paint deposits. The composition of the present invention has significant utility for cleaning lines, tanks, nozzles and hoses of paint delivery systems. The composition also may be utilized to clean paint residues from spray booths, conveyors and paint formulating equipment. In addition, the composition may be utilized as a paint stripper. These and other advantages of the present invention will be readily apparent from the description, discussion and examples which follow.